• Journal of Electrical Engineering and Technology
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• 제11권3호
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• pp.781-789
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• 2016

Busbar has been used as electric conductor within extra high voltage (EHV) gas insulated switchgear (GIS), which makes EHV GIS higher security, smaller size and lower cost. However, the main fault of GIS is overheating of busbar connection parts, circuit breaker and isolating switch contact parts, which has been already restricting development of GIS to a large extent. In this study, a coupled magneto-flow-thermal analysis is used to investigate the thermal properties of GIS busbar in steady-state. A three-dimensional (3-D) finite element model (FEM) is built to calculate multiphysics fields including electromagnetic field, flow field and thermal field in steady-state. The influences of current on the magnetic flux density, flow velocity and heat distribution has been investigated. Temperature differences of inner wall and outer wall are investigated for busbar tank and conducting rod. Considering the end effect in the busbar, temperature rise difference is compared between end sections and the middle section. In order to obtain better heat dissipation effect, diameters of conductor and tank are optimized based on temperature rise simulation results. Temperature rise tests have been done to validate the 3-D simulation model, which is observed a good correlation with the simulation results. This study provides technical support for optimized structure of the EHV GIS busbar.

• 조명전기설비학회논문지
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• 제20권7호
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• pp.14-20
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• 2006

본 연구는 위치지정 중첩 화상표시 구동방식에서 표시방전 유지펄스의 휴지기간 폭에 대한 방전특성을 실험한 것이다. 실험결과, 표시방전은 벽전하 뿐만 아니라 공간전하의 영향도 강하게 받는다는 것을 알았다. 휴지기간 바로 다음에 나오는 첫 번째 표시방전은 휴지기간에 대한 의존도가 높으며 두 번째 표시방전은 의존도가 매우 낮았다. 첫 번째 표시방전이 다소 불충분해도 어느 정도이상 벽전하가 축적되기만 하면 두 번째 표시방전은 안정적으로 유도될 수 있으나 공간전하의 영향을 고려하면 휴지기간의 폭은 $30[{\mu}s}]$ 이내가 바람직하다. 또한 휴지기간의 폭이 $30[{\mu}s}]$까지는 약 12[V]의 균일한 표시방전 전압의 동작마진을 얻을 수 있었다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2000년도 제1회 학술대회 논문집
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• pp.57-58
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• 2000

we have grown vertically aligned carbon nanotubes on a large area of Co-Ni codeposited Si substrates by thermal chemical vapor deposition using $C_2H_2$ gas. The carbon nanotubes grown by the thermal chemical vapor deposition are multi-wall structure, and the wall suface of nanotubes is covered with defective carbons or carbonaceous particles. The carbon nanotubes range from 50 to 120 nm in diameter and about 130 ${\mu}m$ in length at $950\;^{\circ}C$. Steric hindrance between nanotubes at an initial stage of the growth forces nanotubes to align vertically. The turn-on voltage was about 0.8 $V/{\mu}m$ with a current density of 0.1 ${\mu}A/cm^2$ and emission current reveals the Fowler-Nordheim mode.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.75.2-75.2
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• 2013

Atomic layer deposition (ALD), utilizing self-limiting surface reactions, could offer promising perspectives for future efficient energy conversion devices. The capabilities of ALD for surface/interface modification and construction of novel architectures with sub-nanometer precision and exceptional conformality over high aspect ratio make it more valuable than any other deposition methods in nanoscale science and technology. In the context, a variety of researches on fabrication of active materials for energy conversion applications by ALD are emerging. Among those materials, one-dimensional nanotubular titanium dioxide, providing not only high specific surface area but also efficient carrier transport pathway, is a class of the most intensively explored materials for energy conversion systems, such as photovoltaic cells and photo/electrochemical devices. The monodisperse, stoichiometric, anatase, TiO2 nanotubes with smooth surface morphology and controlled wall thickness were fabricated via low-temperature template-directed ALD followed by subsequent annealing. The ALD-grown, anatase, TiO2 nanotubes in alumina template show unusual crystal growth behavior which allows to form remarkably large grains along axial direction over certain wall thickness. We also fabricated dye-sensitized solar cells (DSCs) introducing our anatase TiO2 nanotubes as photoanodes, and studied the effect of blocking layer, TiO2 thin films formed by ALD, on overall device efficiency. The photon convertsion efficiency ~7% were measured for our TiO2 nanotubebased DSCs with blocking layers, which is ~1% higher than ones without blocking layer. We also performed open circuit voltage decay measurement to estimate recombination rate in our cells, which is 3 times longer than conventional nanoparticulate photoanodes. The high efficiency of our ALD-grown, anatase, TiO2 nanotube-based DSCs may be attributed to both enhanced charge transport property of our TiO2 nanotubes photoanode and the suppression of recombination at the interface between transparent conducting electrode and iodine electrolytes by blocking layer.

• 대한산업공학회지
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• 제38권3호
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• pp.220-226
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• 2012

The Electric discharge machining (EDM) process is used to minimize the difference between designed feature and machined feature while the most workpiece is removed through the cutting processes. The tiny-deep hole machining and perpendicular wall machining in mold and die are good applications of EDM. Among EDM equipment, the super drill uses the hollowed electrode to eliminate the debris which causes the second discharge with the electrode and degrades the machining quality. Through the hollow, the high pressured discharge oil is supplied to remove the debris together with the spindle rotation. The thin-hollow electrode tends to easily wear out compared to the sold die-sinking electrode and its wear rate is might not allowed to monitor in real time during discharging. Up to now, the wear amount is measured by off line method, which leads machining time to increase because the hole pass-through moment can be check by visual (manually) with the extra tool path. Therefore, this study suggests the attractive method to evaluate the hole pass-through moment in which the gap voltage and z-axis encoder pulse are monitored to predict the moment. The commercial super drill is used to validate the proposed method and the experiment is carried out.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
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• pp.575-578
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• 2004

The charging tendency of $Zn_2SiO_4:Mn^{2+}$ phosphor surface was modified in order to improve discharging characteristic of green cell in an ac-plasma display panel (ac-PDP). The Zinc-silicate ($Zn_2SiO_4:Mn^{2+}$) green-emitting phosphor was coated with magnesium oxide(MgO), which is viable to have positive charge on the surface. After fabricating the green cell with MgO-coated $Zn_2SiO_4:Mn^{2+}$, the electrical and optical properties in the cell were examined. It was found that the dynamic voltage margin could be increased while the address time was reduced. It may be ascribed to the change of charging tendency of $Zn_2SiO_4:Mn^{2+}$ phosphor by MgO coating, which makes it possible to stable wall-charge accumulation. When $Zn_2SiO_4:Mn^{2+}$ phosphor was coated with 1.3wt%-MgO, the address time was reduced 1.2 ${\mu}s$ and the address voltage lowered 25 V without any misfiring problem, compared to those of typical $Zn_2SiO_4:Mn^{2+}$ phosphor layer. The luminescence intensity of green cell using MgO-coated phosphor layer was also improved by 10%.

• Clinical and Experimental Pediatrics
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• 제61권9호
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• pp.271-278
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• 2018

Purpose: Abnormal potassium channels expression affects vessel function, including vascular tone and proliferation rate. Diverse potassium channels, including voltage-gated potassium (Kv) channels, are involved in pathological changes of pulmonary arterial hypertension (PAH). Since the role of the Kv1.7 channel in PAH has not been previously studied, we investigated whether Kv1.7 channel expression changes in the lung tissue of a monocrotaline (MCT)-induced PAH rat model and whether this change is influenced by the endothelin (ET)-1 and reactive oxygen species (ROS) pathways. Methods: Rats were separated into 2 groups: the control (C) group and the MCT (M) group (60 mg/kg MCT). A hemodynamic study was performed by catheterization into the external jugular vein to estimate the right ventricular pressure (RVP), and pathological changes in the lung tissue were investigated. Changes in protein and mRNA levels were confirmed by western blot and polymerase chain reaction analysis, respectively. Results: MCT caused increased RVP, medial wall thickening of the pulmonary arterioles, and increased expression level of ET-1, ET receptor A, and NADPH oxidase (NOX) 4 proteins. Decreased Kv1.7 channel expression was detected in the lung tissue. Inward-rectifier channel 6.1 expression in the lung tissue also increased. We confirmed that ET-1 increased NOX4 level and decreased glutathione peroxidase-1 level in pulmonary artery smooth muscle cells (PASMCs). ET-1 increased ROS level in PASMCs. Conclusion: Decreased Kv1.7 channel expression might be caused by the ET-1 and ROS pathways and contributes to MCT-induced PAH.

• 한국진공학회지
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• 제11권2호
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• pp.127-134
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• 2002

본 논문은 AC PDP에서 사용하는 가스의 혼합비, 압력, 페닝 효과를 고려한 가스 조합의 최적화를 통해 낮은 방전전압으로 휘도의 증가를 얻을 수 있는 고휘도, 고효율 PDP 페닝 기체 혼합비를 찾고자 하였다. He(70%)-Ne(27%)-Xe(3%)의 3원 혼합기체와 Ne(96%)Xe(4%)의 2원 혼합기체에 페닝 효과를 극대화하기 위한 소량의 Ar, Kr을 첨가하여 각각의 첨가비에 따른 방전 개시전압, 방전 유지전압, 휘도, 발광효율 등을 측정하였다. 또한 페닝효과에 의한 방전 공간상의 전자수 증가를 확인하기 위해 셀 내의 전극 위에 쌓이는 벽전하 양을 측정하였다. 소량의 Ar(0.01%-0.03%) 또는 Kr(0.01%-0.03%)을 HE-Ne-Xe과 Ne-Xe 혼합가스에 첨가했을 때 페닝효과에 기인하여 휘도 및 발광효율이 각각 최고 10%-20% 증가하였다. 또한 페닝효과를 확인하기 위한 벽전하의 양은 10%-25% 증가를 보였다. 방전개시전압 및 최소방전유지전압은 대략 2V-3V정도 감소하였다.

• Journal of Electrical Engineering and Technology
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• 제13권5호
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• pp.2059-2066
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• 2018

This study explored the feasibility of utilizing an SWCNT-coated fabric sensor for the development of a wearable motion sensing device. The extent of variation in electric resistance of the sensor material was evaluated by varying the fiber composition of the SWCNT-coated base fabrics, attachment methods, number of layers, and sensor width and length. 32 sensors were fabricated by employing different combinations of these variables. Using a custom-built experimental jig, the amount of voltage change in a fabric sensor as a function of the length was measured as the fabric sensors underwent loading-unloading test with induced strains of 30 %, 40 %, and 50 % at a frequency of 0.5 Hz. First-step analysis revealed the following: characteristics of the strain-voltage curves of the fabric sensors confirmed that 14 out of 32 sensors were evaluated as more suitable for measuring human joint movement, as they yield stable resistance values under tension-release conditions; furthermore, significantly stable resistance values were observed at each level of strain. Secondly, we analyzed the averaged maximum, minimum, and standard deviations at various strain levels. From this analysis, it was determined that the two-layer sensor structure and welding attachment method contributed to the improvement of sensing accuracy.

• 한국전기전자재료학회논문지
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• 제35권6호
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• pp.594-602
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• 2022

Cast-resin transformers are widely installed in various electrical power systems because of their low operating cost and low influence on external environmental factors. However, when they have an internal defect during the manufacturing process or operation, a partial discharge (PD) occurs, and eventually destroys the insulation. In this paper, a Rogowski-type PD sensor was studied to replace commercial PD sensors used for the insulation diagnosis of power apparatus. The proposed PD sensor was manufactured with four different types of PCB-based winding structures, and it was analyzed in terms of the detection characteristics for standard calibration pulses and the changes of the output voltage according to the distance. The output increased linearly in accordance with the applied discharge amount. It was confirmed that the hexagon structure sensor had the highest sensitivity, because the winding cross-sectional area of the sensor was larger than others. In addition, as the distance from the defect increased, the output voltage of the sensors decreased by 7.32% on average. It was also confirmed that the attenuation rate according to the distance decreased as the input discharge amount increased. For the application of this new type sensor, PD electrode system was designed to simulate the void defect. Waveforms and PRPD patterns measured by the proposed PD sensors at DIV and 120% of DIV were the same as the results measured by MPD 600 based on IEC 60270. The proposed PD sensors can be installed on the inner wall of the transformer tank by coating its surfaces with a non-conductive material; therefore, it is possible to detect internal defects more effectively at a closer distance from the defect than the conventional sensors.